This Core Section proposal describes the advantages which will accrue to the investigations which are components of this Program Project application. The 7 component projects are directly linked by virtue of common human milk donors and samples. Included in this Core Section are descriptions of (1) the logistics of sample collection, (2) the acquisition of a demographic data base for subsequent correlation with results of various assays to be performed on the milk samples (as well as other tissues), and (3) a shared computer-based system of data collection, storage, and analysis. The epidemiologists, computer programmer, and nurse specialists will function as core resource workers for all investigators included in this Program Project.